We are continuing our efforts to purify SV40 small t antigen from clone of E. coli. which synthesizes relatively large quantities of this protein. We are also beginning to evaluate the quantity of t produced in monkey cells infected with an adeno-SV40 hybrid virus - PARA - which greatly overproduces the large SV40 T antigen. The SV40 early region of this virus is presumably governed by the major adeno late promoter. If t is also overproduced, we shall attempt to purify it from PARA-infected cells as well. Once pure t is available, we shall attempt to decipher major elements of its function in virus-infected cells.